Correct. Autonumber only records record count, not record order.
Because Airtable is more database than spreadsheet, records have no inherent knowledge of other records. Order is maintained as you drag records around, but Airtable only makes the order available to scripts that request records from a specific view. While it’s not possible to trigger an automation—which could run a script to number the records based on order—simply by changing the record order, you could trigger such an automation using other means. You could also run a similar script manually from the Apps sidebar.